A probe for a surgical instrument used for cutting selected tissue in a body cavity while under visual inspection, e.g., a surgical tool for the release of the transverse carpal tunnel ligament, has a profile where the flat top surface of the probe has a wider width dimension than the lower surface of the probe. Thus, the sides of the lower surface are sloped or curved inward such that all points below the flat top surface at any particular point on the first and second sides of the flat top surface have a width that is smaller than the width dimension of the flat top surface. The degree of sloping or curving inward will cause tissues to be moved downward (instead of upward) when the probe is inserted, and will provide for generating an upward force that firmly holds the probe against the tissue to be cut and a downward force on the surrounding tissue below the probe.